Phrase used to describe to action of taking a deep breath, forgetting about the pain and fear, digging down deep, and carrying on to the end.

Dad: Son, are you injured or are you hurt?

Son: What's the difference?

Dad: If you are injured, you sit your ass on the sidelines and watch your team play the rest of the game. If you are hurt, you cowboy the fuck up, swallow your pain, put your helmet back on, and get back into the fight.